1. Field of the Invention
The present invention relates to a textile machine which can be used for deknitting yarns, in particular a machine which can be used to deknit elastomeric yarns from a knitted tape of elastomeric yarns in such a manner as to uniformly apply tension on each end being deknitted.
2. Background of the Invention
In the field of textile manufacturing and in particular in the practice of spandex yarn production, it has become a common practice to knit a tape of elastomeric yarns. This practice has proven advantageous in that it provides manufacturers with a method of delivering multiple ends of the elastomeric yarns in a convenient way to narrow fabric manufacturers without having to resort to the installation of creels and individual tensioning/controlling devices for each yarn end. The practice results in significant savings to the manufacturers in space and creeling preparation time.
It is common in the preparation of a tape of elastomeric yarns to employ textile machines for making narrow elastic fabric receive and knit together a plurality of elastic and conventional yarn ends from a number of incidental yarn packages mounted on large creel frames adjacent to the machine. This practice of knitting a plurality of elastic yarn ends into a compact knitted yarn package or tape which must subsequently be deknitted during the feeding operation has proven effective to reduce the floor space required for the yarn supply arrangement and, in addition, to improve the efficiency and ease of transporting the yarn. Examples of such yarn packages are disclosed in U.S. Pat. Nos. 3,827,261, 4,411,142 and 5,569,212. These methods of handling yarn have proven especially useful for elastic yarn, such as spandex, which may shrink, take a permanent set, or distort the yarn package during storage when handled conventionally, thereby presenting problems of non-uniform tension, snarling, and the like when the yarn is fed to the textile fabric making machine.
Attempts to use knitted yarn packages of highly elastic yarns of relatively high denier has resulted in numerous problems. Early efforts required undesirably low feeding speeds which resulted in significant economic losses over a period of time in view of the capital investment in modern, high-speed, textile fabric forming machines since the slow speed of deknitting did not permit the operator to take full advantage of the production capacity of the high speed machines.
U.S. Pat. No. 3,542,084 provided a device for feeding and unraveling a knitted yarn package. In that device, a separate advancing mechanism passes the strip from the knitted yarn package through a pair of feed rolls. The motor driving the rolls is controlled by a relay activated by an electrically conductive finger which rests above the advancing yarn strip and a grounded bracket below the yarn strip. When the yarn unravels past the point where it is no longer between the finger and the bracket, the relay is activated, thereby causing the motor to turn the feed rolls.
Such a device has proven to have certain disadvantages. First, if used with a yarn package having a plurality of ends, a single, incompletely unraveled yarn end could prevent the finger from contacting the bracket, thereby preventing the feed rolls from advancing the knitted yarn package. Second, no means are provided for controlling the tension as the strip is advanced. Third, no means are provided for adding tension over the amount necessary to cause the knitted yarn package to unravel. Finally, the design, as shown in FIG. 3 of the '084 patent, is not easily adaptable for feeding a modern textile fabric forming machine which is capable of using a plurality of knitted yarn packages and, consequently, would require a number of feeders for each textile machine.
Another well-known apparatus which has previously been adapted for feeding knitted yarn packages is illustrated in U.S. Pat. No. 2,920,772. This apparatus commonly referred to as a "mousetrap" includes a plurality of parallel pins aligned perpendicular to the direction of movement of the knitted yarn package as it moves towards the textile fabric making machine. The pins are mounted alternatively to an upper, pivoting member and a lower stationary base member. The knitted yarn package is then passed between the plurality of pins. Tension is added by adding weight to the upper pivoting member to cause the pins mounted thereto to press against the moving knitted yarn package, thereby increasing the resistance to movement of the knitted yarn package.
Another device which is similar to the "mousetrap" device is commonly referred to as a "ladder". This device also includes a plurality of parallel pins; however, unlike the "mousetrap" device, the pins are arranged similarly to rungs on a ladder. The knitted yarn package is then threaded over and under as many rungs as needed to provide sufficient tension to unravel the knitted yarn package.
Certain disadvantages are also apparent with both of these designs. First, no means are provided for ensuring uniform tension across the width of the knitted yarn package resulting in one or more yarn ends being under more or less tension than the other. Thus, the amount of these latitudinal tension variations may cause the fabric produced by, for example, a knitting machine, to skew since the amount of tension through one portion of the fabric may differ from the remainder of the fabric. Second, no means are provided for controlling the tension in the direction of movement of the knitted yarn package after the tension initially has been set. Thus minor changes in the textile fabric making machine's feed speed may result in differences in the amount of this longitudinal tension that may cause the pick count of the finished fabric to fall outside of prescribed limits. Furthermore, larger changes in the feed speed may result in breakout (i.e., the amount of tension exceeds the breaking strength of the yarn end) or "blow-up" (i.e., the amount of tension is less than the force needed to unravel the knitted yarn package and some incompletely unraveled yarn ends actually enter the fabric, making machine). A common problem associated with the use of the standard ladder device in deknitting operations is the constant surging of the tape being fed into the device.
U.S. Pat. No. 4,870,839 is a deknitting device similar to the "mousetrap" and "ladder" devices but employing a support member upstream of the textile fabric making machine and generally perpendicular to the direction of movement of the yarn ends towards the machine. The support member of '839 patent engages the yarn ends prior to the yarn ends being absorbed by the device in an effort to enhance unraveling the knitted yarn package. Th'839 deknitting device further relies on the unraveling function of a plurality of bristles mounted on a rotating cylinder, the rotation of which is coordinated with the speed of the receiving textile machine by a belt drive. This complicated device, like the conventional deknitting devices described above, fails to solve the critical problems of uneven tension on the tape being deknitted and the related problem of surging of the tape due to high and uneven tension.
It is therefore desirable to develop an apparatus for feeding a knitted yarn package having a plurality of yarn ends to a textile machine for knitting narrow elastic fabric that will uniformly unravel the knitted yarn package. In addition is has become desirable to develop an apparatus for feeding a knitted yarn package that will apply substantially uniform and constant tension to the yarn ends being fed to the machine even if the speed of the machine changes, thus overcoming the aforementioned problems associated with conventional deknitting devices. Finally it has become desirable to develop such an apparatus which is simple to install, use and maintain.
For the above reasons, the requirement for an effective deknitting device is of paramount importance. Critical to the effectiveness of a deknitting device is the uniform deknitting of the tape and the application of uniform tension on each yarn end being deknitted.